The art has had difficulty in providing for pressure-tight connections for systems requiring relative rotary motion at pipe joints; for example, in solar energy systems which continuously rotate to track the solar movement, or in rotary drive systems where a pressurized fluid must be conveyed to a rotating circumferential surface from a stationary hub, maintaining a pressure-tight seal at the line of relative movement has not been wholly successful. In many such situations it is desirable, or necessary, to maintain the seal over lengthy period of time, when wear becomes a problem, or to avoid contamination of the fluid.